The present invention relates to an image processing apparatus, an output apparatus, an image processing system and an image processing method arranged to perform a banding process such that a process for dividing objects across bands is performed so that an image is directly drawn on a band buffer without a necessity of generating an intermediate language.
An output apparatus for interpreting print data supplied from a host side application to produces an output of an image on a printing sheet or the like generally incorporates a work memory required to convert print data into a raster scan type format and a memory to serve as an output buffer for storing converted raster data. In particular, the output buffer must have a large memory capacity because raster data obtained by raster development must be stored. Therefore, a major portion of the output apparatuses is structured to perform a process for dividing one page in a sub-scanning direction into a plurality of regions which are called bands. Moreover, raster data is generated for each band. The foregoing process for reconstructing print data in band units is called a banding process which is well known.
The above-mentioned conventional image processing systems required to reduce the memory capacity of the output buffer have been adapted to the following method.
For example, an image processing system is known in which PDL data is converted into intermediate format data by an output apparatus, followed by developing intermediate format data into raster data on the output buffer. In the foregoing case, the capacity of the output buffer can be reduced because the raster development can be performed in band units.
Another image processing system is known which has the steps of causing a host-side apparatus to generate raster data for each band and causing an output apparatus to store raster data in band units. Also an image processing system is known in which intermediate format data for each band is generated by the host-side apparatus. Moreover, the output apparatus raster-develops intermediate format data. Also in the above-mentioned cases, raster data can be generated in band units so that the reduction in the capacity of the output buffer is permitted.
However, the image processing system, which has the structure that the host-side apparatus generates PDL data and the output apparatus generates intermediate format data so that the banding process is performed, cannot reduce the load which must be borne by the output apparatus. Therefore, there arises a problem in that long waiting time is required until a printing process is completed if a plurality of host apparatuses simultaneously make demands to perform printing operations. If PDL data relates to an image, the foregoing system is required to convert image data into an intermediate code and to store original image data until original image data is raster-developed. The data capacity of image data is considerably larger as compared with text data and graphics data. Therefore, image data is usually compressed when it is stored. Another problem arises in that a memory must be provided which temporarily stores image data in order to perform the compressing process.
The system structured to cause the host-side apparatus to perform the banding process to generate raster data and the system causing the host-side apparatus to perform the banding process to generate intermediate format data cannot reduce the load which must be borne by the host-side apparatus. Therefore, there arises a problem in that long waiting time is required to receive a next instruction from input of a print command to the host-side apparatus.
A portion of the output apparatuses incorporates individual trays for the portrait direction and the landscape direction even if the sizes of the printing sheets are the same. In a case where the foregoing output apparatus encounters a case in which either of the trays has no paper sheet, it is convenient if paper sheets in another tray can be used to continue the printing operation. However, since the band is formed by dividing one page in the sub-scanning direction, the printing process cannot be performed by using the paper sheets in the other tray if the banding process is performed by the host-side apparatus.